I've used Google Spreadsheet as an "API" before (manually, not using this wrapper), and it is definitely not made to be used as such. Under heavy load, it slows down or times out, and even under the best circumstances it's not exactly fast. It's great in a pinch. My use-case was a spreadsheet that others in my organization wanted to edit, then we'd pull the data onto a web page and display nicely. It worked, but even…
Secondly, while the load page and then load the data in as JS approach definitely works, I found that just pushing the data in as HTML on the server side was easier to cache and faster to load.
1 - https://gist.github.com/mbuckbee/0ad3bd150e705c769c50
This was sufficient to handle thousands of requests per hour with a page load time of less than 250ms